Direct fired unit heater



April-26, 1938. .H C, ANDERSON `2,115,057 .l

DIRECT FIEED UNIT HEATER Filed Jan. 3l, 1936 y 2 She'ats-Sheei l INVENTOR.

W. y?, A l HATTORNEYJ.

WITNEJSES April 26, 193s. Y H. C. ANDERSQN 2,115,057

DIRECT FIRED UNIT HEATER Filed- Jan. 31, 1956 2 Sheets-Sheet 2 INVENTOR.

ATTORN E Y6.

Patented Apr. 26', 19,38

UNIT-ED STATES PATENT OFFICE DIRECT FIRED UNIT HEATER Harold C. Anderson, Pittsburgh, Pa., assignor to Bravo Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application January 3?., 1936, Serial No. 61,696

6 Claims.

This invention relates to direct red unit heaters, and more particularly to those through which air from a space to be heated is posltivelycirculated.

Unit heaters of the type referred to herein are particularly suitable for heating large spaces such as steel mills, garages, factory buildings and the like. They consist of a combustion chamber in which a very high temperature is maintained by '10 any suitable fuel, an air duct surrounding the chamber, and means for forcing cool air from the space to be heated through the air duct and out of the heater in heated condition. It has been found, however, that even with the wall of `the combustion chamber corrugated so as to increase its heat radiating area, these heaters have been inefficient in transferring heat from .the combustion chamber walls to the current of air circulated through the heaters. Furthermorewhen vthe heaters are maintained at the high temperatures at which they are supposed to operate,y the inetal walls of the combustion chambers soon vburn through.

It is among the objects of this invention to provide a direct fired unit .heater of simple and inexpensive construction which is highly ecient in heating air forced through it, and the metal combustion chamber walls of which do not burn out.

The invention is illustrated in the accompanying drawings in which Fig. l is 'a s ide view of a unit heater broken away at its opposite ends in three different vertical planes to show its interior construction; Fig. 2 isa vertical section taken on line II-II of Fig. l and showing an end wall of the combustion chamber;'Fig. 3 is a vertical section taken on the line III-II of Fig. 1; Fig. 4 is an enlarged perspective View of a deflector plate A of the type shown in the preceding figures; and

4,0 Figs. 5 and 6 are two modifications of the deecto-r plate;

Referring to the first three figures of the drawings, a trough-like fire-box l is built up of refractory material on a platform oroor 2 supported on the central portion of an elevated frame' 3 which is mounted on legs 4 at its corners. A metal casing 5 is mounted on the edges of floor 2 for enclosing the fire-box with which it forms a furnaceprovided with a combustion chamber.

The casing in cross section is preferably inthe shape of an inverted U with its side walls spaced from the rc-box. Ihe sides and top of the casing are preferably corrugated to increase its heatabsorbing and radiating surface area, but its endY walls may beat plates 6 through one of which a portion of the nre-box projects (Fig. 1'). This portion is provided with an opening 'l through which fuel is introduced for combustion in the nre-box. If desired, an oil or gas burner, not shown, can be mounted in this opening. 5 The gases in the combustion chamber are drawn downwardly between the brickwork of the fire-box and the corrugated casing, beneath the fire-box through ues 8, and out of the furnace through breaching 9 by an exhauster fan il v1() adapted to be connected to the usual stack. "This fan is driven by a shaft l2 rotated by an electric motor i3 which can be mounted at the opposite end of the heater, as show-.fz in Fig. l.

The furnace casing i's entirely surrounded by l5 a metal shell l@ which is of the/same general shape as the casing, but is larger so as to rest on frame 3 beyond floor 2 and provide air spaces or ducts between itself and the side and end walls of the casing. Preferably, as shown in Fig. 2, 20 casing end wall plates 6 extend outwardly to the shell to which they are connected. Mounted below frame 3 is a plurality of suction fans or blowers I6 driven by shaft l2 for drawing in cool air fram the space to be heated and forcing it up 25 through the spaces betweeniloor 2 and the shell at one side of the heater and into the air ducts surrounding the casing. At the opposite side of the heater the spaces between the shell and furnace floor forml outlets for the air ducts and com- 30 municate, preferably by three outlet nozzles I1, I8 and i9, with the space being heated. Any suitable means for directing the flow of heated air issuing from these nozzles may be incorporated therein. f, l

It is a feature of this invention that means is provided for directing the air, being circulated by the blowersthrough the air ducts of the heater, against the hot metal casing 5 so as to absorb more heat therefrom. Accordingly, a plurality 40 of deflector plates is mounted on the outer surface of the top and side walls of the casing, thev plates being formed for directing the circulating' air inwardly against the casing. Preferably, each plate is of metal and consists of a fin portion 2l 45 projecting outwardly at right angles to the casing to which its innerfedge is welded or otherwise secured. As shown in Fig. 4,-the outer portion of the plate is` bent atright angles and cut away from the n'for a portion of its length to provide 50 a deilector portionA 22 that is curved outwardly. The plates are preferably mounted in staggered relation on the outwardly extending corrugations only of the furnace casing with their deector portions overlying the inwardly extending corru- 55 same time preventing the casing from .bcoming overheated and burning out. v 'I'o remove still more heat from 4the combustion chamber Vand conduct it into the chamber wall, a plurality of" metal fins 23 is preferably secured to all of the casing corrugations between the casing and the fire-box side walls, as shown in Figs.l 1 and 3. The hot furnace gases are drawn by the exhauster' past these inside ns to which they give oiI a considerable amount of their heat.

The deector plates are also mounted on end plates 6 of the furnace casing where they deflect the circulated air against the end plates, and radiate heat from the end plates fast enough to prevent them from burning out from the intense heat in the combustion chamber. Also, the deilector plates are preferably arranged in the manner shown in Fig. 2 so as to direct the in- 1 coming air diagonally upwardly and across the end plates at their hottest part which is immediately above the nre-box. For this purpose the deector plates on the air inlet side are inclined inwardly and upwardly, While the uppermost defiectors are mounted for holding the air down away from the tops of the end plates which are much cooler than the portions directly below.

In Fig. 5 a deilector plate is shown which is formed from a flat metal iin 26 to the lower end ,of the outer edge of which a small plate 21 is lconnected. The plate extends below the iin and lis curved outwardly for deflecting air inwardly across the fin.

The detlector plate shown in Fig. 6 is similar to that shown in Fig. 4, with the exception that the laterally bent portion 28 is cut away from the iin portion 29 for the major part of its length. The

cut-away portion is bent outwardly in a plane oblique to the remainder of the laterally bent portion.

A direct red unit heater constructed in accordance with this invention is very eilicient because the air circulated through it is caused to scrub against the hot combustion chamber wall and absorb heat therefrom. The deector plates likewise break up the air stream, causing a turbulence that brings all of the air into contact with the hot surfaces. Another advantage is that intense heat can be maintained in the combustion chamber without danger of burning out the chamber walls, because the deilectcr plates radiate heat outwardly from those walls fast enough to prevent them from burning.

According to the provisions of the patent statutes, I have explained the principle and construction of my invention and have. illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise n than as specifically illustrated and described.

I claim:

1. A direct red unit heater comprising a shell, a vmetal furnace'v casing disposed therein and forming a combustion chamber in which heat is produced for heating the casing,'.the side and end walls of said casing being spaced from said shell, means for forcing a current of air Iupwardly at one side of said unit in the spaces 'between said.

shellA and casing-side-and end walls, the opposite side of said unit'being provided adjacent the bottom of the shell with outlets for heated air, rand a plurality of deilector plates mounted on the outer surface of said casing end walls, said plates on the air inlet side of said unit being inclined inwardlyand upwardly to direct rising air across the central portions of said end walls, and the plates on the air outlet side of said unit extending substantially vertically.

2. A direct fired unit heater comprising a shell, a metal furnace casing disposed therein and forming a combustion chamber in which heat is produced for heating the casing, the side and end walls of said casing being spaced from said shell,

means for forcing a current of lair upwardly at one side of said unit in the spaces between said shell and casing side and end walls, the opposite side of said unit being provided adjacent the bottom of the shell with outlets for heated air, and a plurality of deflector plates mounted on the outer surface of said casing end walls, said plates on the air inlet side of said unit being inclined inwardly and upwardly to direct rising air across the central portions of said end walls, and the plates on the air outlet side-of said unit extend-. ing substantially vertically, and said plates having laterally extending portions turned outwardly away from said end Walls for directing said air inwardly against the end walls.

3. A direct red unit heater comprising a shell, a metal furnace casing disposed in the shell and spaced therefrom with its side walls provided with vertical corrugations extending across the top of the casingmeans for forcing a current of air upf wardly at one side of said unit in the spaces between sald shell and the side and end walls of the casing, a plurality of relatively.v short deilector plates mounted on said casing side walls in substantially straight parallel lines extending vertically of said side walls and across the top of the casing for directing said air against the casing.

vertical corrugations extending across the top of the casing, means for forcing a current of air upwardly at one side of said unit inthe spaces between said shell and the side and end walls of the casing, a plurality of relatively short deector plates mounted on said casing side walls in substantially straight parallel lines extending vertically of said side walls and across the top of the casing for directing said air against the casing, the deilector plates in each line being staggered relative to the plates in the adjacent lines and a plurality of deector plates mounted -on the outer surfaceof said casing end walls, said end wall plates on the air inlet side of said unit being inclined inwardly and upwardly to direct rising air across the central portions of s'aid end walls.

5. A direct red unit heater comprising a shell, a metal furnace casing disposed in the shell and spaced therefrom with its side Walls provided with vertical corrugations extending across the top of Vthe casing, means for forcing a current of air between said shell and the side and end walls of the casing,` the opposite side of said unit beingl provided adjacent the bottom of said shell with an outlet for heated air, a plurality of rdeilector plates mounted on said casing side walls for di recting said air against the casing, a plurality of deiiector plates mounted on the outer surface of said casing end walls, said end wall plates on the air inlet side of said-unit being inclined inwardly and upwardly to direct rising air across the central portions of said end walls, and a plurality 4of/metal ns mounted on the inner surface of the casing to conduct heat to the casing.

HAROLD C. ANDERSO. 

